Traditional telephony service profiles are typically associated with devices, not users. The device (and device identity) may be used as a proxy for the user. Traditional telephony services associated with a particular device are then usually tied to a particular service profile. For example, when a mobile device registers with a network, the authentication/authorization process verifies the user's authentication credentials and may attach a service profile to the device based on the Home Location Register (“HLR”)-provisioned information for the user. The HLR is a central database that contains details of each subscriber that is authorized to use the core network. Similar approaches are being adopted on the new Voice over IP (“VoIP”) environments—the Session Initiation Protocol (“SIP”) registration of the device associates the user with a particular service profile. SIP is a protocol developed by and proposed standard for initiating, modifying, and terminating an interactive user session that involves multimedia elements.
SIP-based next-generation networks (“NGN”) are becoming more common in the telecommunications industry. Specifically, the IP Multimedia Subsystem (“IMS”) network is SIP-based NGN for fixed IP and for mobile services. An IMS-based VoIP implementation uses SIP and runs over the standard Internet Protocol (“IP”). SIP is the signaling protocol of the IMS architecture. IMS offers a wide-range of different services, but users may have limited access or flexibility with the set of services available. As IMS or other SIP-based NGNs are likely to become more common in the future, a user will want flexibility in the types of services offered through the architecture.